Food products consisting of a core of filling inside a coating are well known. They can be produced by co-extruding the coating and filling, and then using an iris cutter or diaphragm to encapsulate the filling within the coating as the extrudate is portioned. Such iris cutters are described in U.S. Pat. No. 4,251,201 and U.S. Pat. No. 4,734,024. They typically comprise a number of moveable blades held within a casing or tray and which form an aperture of variable size. The aperture can be opened and closed by sliding or rotating the blades. This type of process is known for encapsulating fillings in various food products, such as dough, as described for example in U.S. Pat. No. 4,734,024. More recently, it has also been applied to produce frozen confections in US 2005/0233033.
However, we have found that further problems arise when an iris cutter designed principally for producing products with an outer layer of dough etc. is used to manufacture products with an outer layer of a frozen confection. Unlike the commonly used encapsulating materials, such as dough, frozen confections are liable to melt. Friction between the blades of the iris cutter causes local heating, which can melt small amounts of frozen confection. The melted frozen confection may then be dispersed onto and/or between the cutting blades where it can remain stagnant. Although the amount of frozen confection that is melted is small, so that the shape of the products is not noticeably affected, it can cause other problems. In particular, in a factory situation, it may not be possible to clean or replace the cutter during a production run of several hours or more. This can result in potential problems due to growth of micro-organisms on the residue of melted frozen confection which could contaminate the products. The present invention lies in the identification and solution of this problem.